CQUeST 2026 Workshop on Cosmology and Quantum Spacetime

Jul 20, 2026, 9:00 AM → Jul 24, 2026, 12:00 PM Asia/Seoul

Babuda Ballroom, 4F, Ocean tower (St. John's Hotel, Gangneung)

Overview

This workshop is an annual event organized by the Center for Quantum Spacetime (CQUeST) in Sogang University. Its goal is to bring together experts in the center’s research areas, including cosmology, modified gravity, string theory, black hole physics, and astroparticle physics phenomenology. CQUeST was first funded by NRF as an outstanding Science Research Center (SRC) from 2005 to 2014. From 2014 to 2020 the center has continued its operation with the support of the individual grants of its members. In June 2020 CQUeST received support as a University Research Center (중점연구소) for additional 9 years. More details about CQUeST can be found at: CQUeST​

Venue

The workshop will be held at the Ballroom Babuda on the 4th floor of the Ocean Tower at St. John's Hotel, Gangneung, Korea.

Program and Timetable

Each day the program of the workshop will consist of invited talks, contributed talks, and CQUeST members' talks. Every participant will have the opportunity to apply for a contributed talk at the time of registration on the workshop website. See timetable.

Registration

Please register until May 31, 2026.

Organizers

Hun Jang (CQUeST)

Junho Hong (CQUeST, Sogang University)

Wontae Kim (CQUeST, Sogang University)

Wonwoo Lee (CQUeST)

Jeong-Hyuck Park (CQUeST, Sogang University)

Stefano Scopel (CQUeST, Sogang University) (Chair)

Tuesday, July 21

9:30 AM → 12:00 PM Session1-Tue

9:30 AM Micro Black Holes may be Dark Matter of the Universe

Primordial black holes (PBHs) are black holes which are believed to have formed in the very early Universe. Recently an idea that asteroid mass PBHs may be dark matter of the Universe is attracting a lot of attention. Their size is icroscopic; they are of the size of a hydrogen atom or smaller.
In this talk, I first briefly review our knowledge about dark matter and black holes, then introduce the idea of micro PBHs as dark matter of the Universe, and discuss how it can be observationally tested. It turns out that gravitational waves are the key to this observational test.

Speaker: Prof. Misao Sasaki (APCTP)

1. PBH=CDM_CQUeST.pdf

10:30 AM Coffee Break

11:00 AM Multi-component Dark Matter from Hidden Gauge Symmetries

Gauge symmetry can naturally accommodate dark matter stability or longevity. Hidden sectors (or dark sectors) with dark gauge symmetry would contain multiple particles , and then multi-component dark matter models become generic. , and they are not an ad hocextension of the WIMP paradigm—it is a natural consequence of a rich hidden gauge sector. Future experiments should search for rich dark sectors rather than minimal dark matter.

Speaker: Prof. Pyungwon Ko (KIAS QUC)

2. CQUeST 2026_고평원.pdf

11:30 AM Spontaneous Leptogenesis in Type I Seesaw

Type-I seesaw models with a spontaneously broken B-L symmetry provide a natural framework for spontaneous leptogenesis driven by a Majoron. The kinetic background of the Majoron acts as a CP-violating source, generating a lepton asymmetry both through the decay of right-handed neutrinos and through equilibration via inverse-decay processes. We construct the Boltzmann equations in a fully consistent manner, incorporating both effects, to enable a quantitative analysis. When the neutrino Yukawa coupling is large enough to maintain B-L violating interactions in thermal equilibrium, the resulting asymmetry closely tracks its equilibrium value. In contrast, when this condition is not satisfied, a nontrivial interplay emerges between decay and inverse-decay dynamics, determined by the Yukawa coupling strength and the initial abundance of right-handed neutrinos.

Speaker: Prof. Eung Jin Chun (Korea Institute for Advanced Study)

3. 260720 EJChun GangNeung.pdf

12:00 PM → 1:30 PM Lunch Break

1:30 PM → 4:00 PM Session2-Tue

1:30 PM Comments on Dynamical Dark Energy

The DESI collaboration interpret a discrepancy in the LCDM parameter Ωₘ at different effective redshifts as a dynamical dark energy signal. I will identify a number of hurdles that need to be cleared before one can fully buy into the claim.

Speaker: Dr Eoin O Colgain (Atlantic Technological University)

4. DESI_cquest_ocolgain.pdf

2:00 PM Long-Lived Heavy Neutrinos from Neutrinophilic Charged Higgs at the HL-LHC

In this talk, I will discuss an alternative production mechanism for long-lived heavy neutrinos within the framework of neutrinophilic Higgs doublet models, where an additional Higgs doublet couples exclusively to the Standard Model (SM) lepton doublets and right handed neutrinos (RHNs). This structure allows the vacuum expectation value (VEV) of the extra Higgs doublet to be much smaller than that of the SM Higgs, thereby generating naturally small Dirac neutrino masses without requiring extremely small Yukawa couplings. A distinctive feature of this framework is the presence of neutrinophilic charged Higgs bosons, which, once produced at the LHC through the Drell-Yan process, decay dominantly into heavy neutrinos and charged leptons. If the heavy neutrinos are sufficiently long-lived, their subsequent decays can give rise to displaced signatures at the LHC. Within the type-I seesaw framework with three RHNs, one of the heavy neutrinos can be long-lived even when it decays through on-shell gauge bosons. In this case, its lifetime is inversely proportional to the lightest neutrino mass while remaining consistent with neutrino oscillation data. I will discuss the displaced-vertex signatures of these long-lived heavy neutrinos produced from neutrinophilic charged Higgs decays at the High-Luminosity LHC. The talk is based on arXiv:2604.00866.

Speaker: Dr Prasenjit Sanyal (CQUeST, Sogang University)

5. Prasenjit_talk.pdf

2:30 PM Dark Photon–Mediated Inelastic Dark Matter: Implications for Cosmology, Astrophysics, and Collider Phenomenology

We explore the phenomenology of the Dark Photon iDM (A'iDM) model, one of the simplest and most direct realisations of the inelastic Dark Matter (iDM) scenario. In this framework, the Standard Model (SM) is extended by a dark sector with an additional U(1)_D gauge symmetry. All SM particles are neutral under this symmetry, which couples to the SM hypercharge gauge boson via a kinetic mixing parameter ε. Our work expands upon existing A'iDM literature in three key ways: we move beyond specific benchmark points, restrict our focus to cosmologically viable configurations, and evaluate the complementarity between accelerator and astrophysical signals. The model features a dark photon A' with mass M_A' and two Majorana states, χ₁ and χ₂, with a mass splitting δ = M_χ₂ - M_χ₁ > 0, where χ₁ serves as the dark matter candidate. By fixing the dark coupling α_D to the electromagnetic coupling α_EM and setting ε to its experimental upper bound, we perform a comprehensive scan of the remaining parameter space (M_χ₁, δ, M_A'). We analyse the χ₁ relic abundance, the prospects for direct and indirect detection, and potential signals at accelerators and in astrophysics. Contrary to suggestions from previous studies that focused on specific benchmarks, our scan shows that α_D = α_EM is not phenomenologically disfavored. We also find that when the χ₁ relic density matches observational data, direct and indirect searches become kinematically inaccessible. However, we show that the projected luminosity of FASER---a dedicated Long-Lived Particle (LLP) detector at the LHC --- can probe or exclude the model's parameter space for M_χ₁ ≲ 7 GeV, 100 MeV ≲ δ ≲ 300 MeV, and M_A' ≲ 25 GeV. This reach could be significantly extended by the proposed FASER 2 upgrade for the High-Luminosity LHC. Interestingly, the parameter space accessible via accelerator LLP searches partially overlaps with the region probed by χ₁ capture in neutron stars. This capture process is expected to heat nearby neutron stars to approximately 2000 K, offering a promising, though challenging, signature for future infrared telescope observations.

Speaker: Dr Abhishek Roy (CQUeST, Sogang University)

6. Abhishek_CQUeST.pdf

3:00 PM Searching for Dark Photon Tridents Through Primordial Black Hole Signatures

The detection of gamma-ray signals from primordial black holes (PBHs) could provide compelling
evidence for their role as a dark matter candidate, particularly through the observation of their
Hawking radiation. Future gamma-ray observatories, such as e-ASTROGAM, and the next-generation
telescopes, are poised to explore this possibility by measuring both Standard Model (SM) and beyond-
the-SM particle emissions. A particularly promising avenue involves production of dark photons by
PBHs, which is a hypothetical particle that decays into photons. In this work, we investigate the
trident decay of dark photons with mass mA′ ≤ 1 MeV focusing on their primary emission from
asteroid-mass PBHs. We assume that the dark photons produced via Hawking radiation decay
into photons well before reaching Earth, thereby enhancing the detectable gamma-ray flux. The
energy spectrum of the photons decaying from the dark photons is distinct from that of direct
Hawking-radiated photons due to higher degree of freedom, leading to observable modifications in
the gamma-ray signal.

Speaker: Prof. Sin Kyu Kang (SeoulTech)

7. 강신규SKKANG_CQUES2026.pdf

4:00 PM → 5:30 PM Session3-Tue

4:00 PM Quadratic effective energy-momentum tensor during Inflation in various gauge conditions

We consider the quadratic effective energy-momentum tensor that plays the role of cosmological back-reaction. We evaluate this from the cosmological perturbations during inflation. We present the recent results in uniform-expansion and uniform-density gauge conditions, and compare with the previous results in other (longitudinal, spatially-flat, comoving) gauge conditions.

Speaker: Prof. Inyong Cho (SeoulTech)

8. QEMT_gauge(Inyong CHO).pdf

4:30 PM Constraining Spatial Curvature with Priors from Swampland Conjectures

We study a string-motivated theoretical prior on the quintessential dark energy model with exponential potential, ( V(φ) = V₀ e^-λ φ ), allowing for non-zero spatial curvature. First, we formulate the corresponding dynamical system and investigate its cosmological evolution numerically, illustrating the phase-space behaviour and the influence of curvature on the background dynamics. In open universes (( Ωₖ > 0 )), it has been suggested that a curvature-related fixed point may support accelerated expansion even for relatively steep potentials compatible with swampland considerations. Next, we explicitly impose swampland-motivated priors on the slope parameter λ, restricting it to values consistent with the de Sitter conjecture that excludes the (curved) ΛCDM limit. Furthermore, we restrict our considerations to the range of field excursion that is consistent with the swampland distance conjecture. Our primary interest is the possibility that such theoretically-motivated priors may shift values of cosmological parameters inferred by observational data, compared with the standard analysis based on theory-agnostic priors such as a sufficiently wide flat prior. We examine this possibility using a combination of Planck CMB data, DESI BAO measurements, and recent Type Ia supernova samples, performing a Bayesian inference of the model parameters. Our analysis indicates that the swampland-motivated prior mildly shifts the values of Ωₖ.

Speaker: Dr Simran Arora (Yukawa Institute for Theoetical Physics, Kyoto University, Japan)

9. CQUeST26_Arora.pdf

5:00 PM Testing O(D,D) string cosmology based on double field theory

The low-energy limit of string theory contains additional gravitational degrees of freedom, the B-field and dilaton, that are not present in general relativity. Together with the metric, these three fields are naturally embedded in the O(D,D)-symmetric framework of double field theory (DFT). Furthermore, extending the O(D,D) symmetry to additional matter fixes a modified minimal coupling in string frame and leads to a DFT version of Einstein's equations, in which the resulting DFT energy-momentum tensor is enhanced to include dilaton pressure and skew-symmetric contributions. After reviewing the DFT formalism, I will explore its cosmological implications: I will describe how homogeneous and isotropic backgrounds can be characterized by two equation-of-state parameters, and I will present some analytic solutions that provide candidate models for bouncing cosmologies. Then I will discuss recent progress toward testing O(D,D) cosmology, including implications for structure formation, luminosity distance measurements, and a possible non-Riemannian origin of the universe.

Speaker: Dr Stephen Angus (CQUeST, Sogang Universtiy)

10. Angus_CQUeST2026.pdf

Wednesday, July 22

9:30 AM → 12:00 PM Session1-Wed

9:30 AM Spacetime picture of strange metal

We introduce field theory version of wormhole in disorder theory and consider the analogy of quantum gravity and disorder theory.

Speaker: Prof. Sang-Jin Sin (Hanyang University)

1. 260722_cquest.pdf

10:30 AM Coffee Break

11:00 AM Dual gravities from entanglement entropy

Applying a rule-based holographic method, we investigate the reconstruction of dual gravity theories from the quantum field theory (QFT) data, specifically entanglement entropy. We first derive a three-dimensional black hole geometry from the entanglement entropy of a two-dimensional thermal system. Using the reconstructed solution, we extract various thermodynamic quantities with small numerical errors. Moreover, we explore how to reconstruct the dual gravity theory beyond the geometry itself. For an undeformed conformal field theory (CFT), we show that the dual gravity theory can be constructed analytically from the analytic form of the entanglement entropy. In particular, we demonstrate how to reconstruct the analytic dual geometry by applying the Abel transformation. Finally, we investigate the numerical reconstruction of the dual gravity theory from numerical entanglement entropy data for a relevantly deformed CFT. After reconstructing the dual gravity, we show that additional information about the renormalization group (RG) flow, for instance, the β-function and the c-function, can be extracted for the considered relevantly deformed CFT.

Speaker: Prof. Chanyong Park (GIST)

2. Dual gravities from entanglement entropy.pdf

11:30 AM Cosmology of ultralight scalar field dark matter

Ultralight scalar field dark matter (ULDM) provides a compelling alternative to the standard cold dark matter paradigm, exhibiting wave-like behavior on galactic and cosmological scales. After a brief review of ULDM and self-interacting ULDM (SI-ULDM), we discuss how SI-ULDM can alleviate the Hubble and S₈ tensions. We also briefly explore possible connections between the SI-ULDM framework, neutrino mass, and the electroweak scale, suggesting a common origin for these phenomena beyond the Standard Model.

Speaker: Prof. Jae-Weon Lee (Jungwon University)

3. CQUEST2026LJW.pdf

12:00 PM → 1:30 PM Lunch Break

1:30 PM → 4:00 PM Session2-Wed

1:30 PM Deep Learning Bulk Spacetime from Boundary Quantum Data

According to the holographic principle—one of the most influential frameworks in contemporary physics—gravitational physics in a bulk spacetime is dual to the quantum physics of a system defined on its boundary. We employ a deep learning approach to reconstruct the bulk spacetime geometry from boundary quantum data, such as conductivity and entanglement entropy. This method offers novel insights into the properties of quantum matter through their dual spacetime interpretation. Because our deep learning approach generalizes to a wide range of problems involving differential equations and integral formulations, it holds broad utility for diverse applications across physics and engineering.

Speaker: Prof. Keun-Young Kim (GIST)

2:00 PM Magnetic Relics from Non-Adiabatic Photon Squeezing during Inflation

We show that inflationary magnetogenesis can occur without modifying the microscopic Maxwell action. The observable photon sector inside a de Sitter causal patch is treated as a reduced subsystem that relaxes at a finite rate toward a horizon-selected quasi-static branch. Because the physical photon frequency continuously redshifts during inflation, this reduced dynamics cannot track the branch exactly and generates a non-adiabatic squeezing of the photon state. The resulting excitation freezes after horizon exit, leaving a magnetic relic that survives reheating as a primordial seed field. For a phenomenologically interesting range of relaxation parameters, the magnetic spectrum is approximately scale invariant to mildly blue, while the associated electromagnetic energy density remains parametrically below the inflationary background. This identifies horizon-induced reduced- state dynamics as a distinct route to primordial magnetogenesis that bypasses explicit conformal- symmetry breaking in the Maxwell sector.

Speaker: Prof. Hyeong-Chan Kim (Korea National University of Transportation)

5. carter_separability.pdf

2:30 PM Near-Extremal Black Holes with Yang-Mills Instantons

We construct black hole solutions in four-dimensional Einstein-Yang-Mills theory with U(2) gauge group. We take a near-extremal limit of the black hole solutions coupled with Yang-Mills instantons which reduces to Witten's multi-instanton solutions described by the Liouville theory in two-dimensional Abelian Higgs model.
We consider a semi-classical quantization of the near-extremal black holes coupled with the Witten instantons in a zero-temperature limit and clarify how zero-modes in gravity and Yang-Mills theory play a crucial role in black hole thermodynamics.

Speaker: Prof. Hyun Seok Yang (GIST)

6. YHS_SGC 2026.pdf

3:00 PM Defect Mass Deformation of ABJM Theory

We study particular gravity duals to the inhomogeneously mass-deformed ABJM (ImABJM) theory. The final goal of this paper is to obtain the ABJM theory deformed by a delta function-type mass. The resultant theory can be interpreted as the ABJM theory with defects. The mass operators of the mass-deformed ABJM (mABJM) theory are identified with these defect operators. Corresponding gravity duals are supergravity solutions obtained by solving a relevant BPS equation. This BPS equation is a linear partial differential equation known as the Helmholtz equation. We solve the differential equation using various numerical methods, including machine learning. We investigate appropriate physical quantities in the supergravity background.

Speaker: Prof. Kyung Kiu Kim (Kookmin University)

7. KimKyungKiu-CQUeST 2026.pdf

4:00 PM → 5:00 PM Session3-Wed

4:00 PM One-loop Partition Functions from Quasinormal Modes and Trace Formulas

One-loop partition functions encode the leading-order quantum corrections to the gravitational path integral and can be constructed from quasinormal modes. We investigate how exact computations of these quantities can be extended beyond highly symmetric backgrounds. Trace formulas provide a powerful framework connecting spectral data of differential operators to geometric data of the underlying manifold. Using generalized trace formulas, we develop a method to compute one-loop partition functions on broader classes of manifolds. We then classify two geometric types whose properties lead to different spectral structures in the corresponding quasinormal modes and one-loop partition functions.

Speaker: Ms Sang-Eon Bak (Arizona State University)

8. CQUeST_Bak.pdf

4:30 PM Primordial Black Holes in Einstein–Dilaton–Gauss–Bonnet Gravity

Primordial black holes (PBHs) provide a unique window into the physics of the early Universe and offer an important avenue for probing gravity beyond General Relativity. In this talk, I will discuss the formation and properties of primordial black holes in the framework of Einstein–Dilaton–Gauss–Bonnet (EdGB) gravity, where a scalar dilaton field is non-minimally coupled to the Gauss–Bonnet curvature invariant. I will present the theoretical motivation for considering this class of modified gravity theories and examine how the Gauss–Bonnet coupling influences the dynamics of gravitational collapse, black hole solutions, and the conditions for primordial black hole formation. I will also discuss the implications of these modifications for the PBH mass spectrum, observational signatures, and constraints from current and future astrophysical and cosmological observations.

Speaker: Dr Madhu Mishra (CQUeST, Sogang University)

9. Madhu.pdf

Thursday, July 23

9:30 AM → 12:00 PM Session1-Thu

9:30 AM Quantum black holes: inside and outside

We revisit the dynamics of black holes using the canonical approach to quantum gravity. By introducing time slices that cover both the inside and the outside of the horizon, we obtain the Wheeler-DeWitt equation. It is not possible to solve it directly, but it is possible to see potential dynamics and boundary conditions. From this, we can conclude that we cannot provide a coherent state that covers both the outside and the inside of the horizon. We will discuss the possible physical meaning of this and apply it to the information loss paradox.

Speaker: Prof. Dong-han Yeom (Pusan National University)

1. Quantum BH.pdf

10:30 AM Coffee Break

11:00 AM Stochastic dynamics from O(2N) fractional Laplacian vector model and O(N) vector model free energy in finite temperature

We explore O(2N) scalar theory with fractional Laplacian, √(-∇²) in d-dimension and its Hamiltonain dynamics which is described by a Schrodinger type equation. This equation is a kind of current conservation equation, where one can define a current j(φ) of a probability P(φ), where φ is the scalar field. Naturally, Gibbs entropy S=-∫ [Dφ] P(φ)log P(φ) can be considered to explore the system. We realize that this Gibbs entropy of the O(2N) scalar theory with fractional Laplacian is matched with free energy of O(N) vector model in finite temperature, 1/β with chemical potnential, μ in d-dimension. The precise map between the stochastic fictitious time t and the inverse temperature β is β=2t. Therefore, the tmeperature dependence of the thermal O(N) vector model can be realized as a dynamics of time dependent solution satisfying Schrodinger type equation. This free energy is obtained by putting O(N) vector model in S¹× R_d, where S¹ is thermal circle with its periodicity β. To get d-dimensional theory, we sum up all possible frequencies on the circle(so called Matsubara frequency summation) which gives d-dimensional thermal partition function. We note that the nontrivial t-dependence appears beyond classical limit.
To take into account quantum effects, we solve the Hamiltonian dynamics by keeping ℏ corrections. The chemical potential is mediated by a parameter l such that μ=log l/β and so we call this l-deformation. This is related to the boundary condition of the Schrodinger equation. We also note that the two theoreis are not equivalent each other and we just check their correspondence in the level of one-loop determinant, i.e. zero point function in the note.

Speaker: Prof. Jae-Hyuk Oh (Hanyang University)

11:30 AM D-instanton effects on the Holographic Weyl semimetals

We investigate D-instanton effects on the holographic Weyl semimetal in a top-down approach. From the free energy of the D7 brane embedding solutions, we get a phase diagram in terms of the electron mass, instanton number, and temperature in the unit of the weyl parameter. We calculate non-linear conductivities from the regularity condition of the probe D7 brane and investigate anomalous Hall phenomena in the boundary system. From the study of the phase diagram, we suggest the gaped phase induced by the instanton to a topological insulator.

Speaker: Prof. Yunseok Seo (Kookmin University)

3. 0720_CQUeST_yseo.pdf

12:00 PM → 1:30 PM Lunch Break

1:30 PM → 4:00 PM Session2-Thu

1:30 PM Scalarized extremal black holes

We study scalarized extremal black holes in the Einstein-Maxwell-scalar theory with two different scalar couplings to two U(1) fields. This theory is inspired by the bosonic sector of N=4 supergravity. Two scalarzied extremal black holes are found with constant secondary scalar hair. We confirm that these are exactly obtained from the standard scalarization and entropy function approach. This implies that it is not easy to find extremal black holes with primary scalar hair.

Speaker: Dr Yun Soo MYUNG (CQUeST, Sogang University)

4. ESBH_CQUeST.pdf

2:00 PM Fortuity and relevant deformation

We investigate the supercharge cohomology of an N=1 relevant deformation of N=4 super Yang-Mills. By introducing a field redefinition, we integrate out massive fields in a cohomological sense. Then, we construct the monotone cohomologies corresponding to the Kaluza-Klein particles of the dual supergravity solution. Some of the monotone cohomologies obey stringy exclusion principle analogous to that of AdS3. Relatedly, they vanish on the diagonal field configurations, unlike N=4 monotone cohomologies. We also construct infinitely many fortuitous cohomologies for gauge group SU(2). We find that unlike N=4 fortuitous cohomologies, they can either be non-vanishing or vanishing on the diagonal fields. By undoing the field redefinition and taking a suitable UV limit, we show that non-vanishing ones reduce to monotone cohomologies of N=4 SYM, while vanishing ones reduce to fortuitous cohomologies of N=4 SYM. This implies that the fortuity can arise due to the relevant deformation, while monotonicity is not.

Speaker: Mr Seunggyu Kim (KAIST)

5. Seunggyu Kim.pdf

2:30 PM Large N Universality of 4d N=1 SCFTs with Simple Gauge Groups

We classify 4d N=1 superconformal field theories arising from asymptotically free simple gauge theories that admit a large N limit, finding 35 families that organize into three universal types according to their large N behavior of central charges. Using this landscape, we test the AdS Weak Gravity Conjecture: the original bound can fail, but a modified bound based on the supersymmetric Cardy formula holds universally — even at finite N. Based on arXiv:2510.19136 and arXiv:2308.01717.

Speaker: Mr Minseok Cho (KAIST)

6. Minseok Cho.pdf

3:00 PM Black hole microstates

I discuss the recent progress on the microstates of the supersymmetric AdS black holes under the AdS/CFT framework. In detail, I will discuss the possible black hole microstates in AdS5 from its dual four dimensional maximal Super-Yang-Mills theory.

Speaker: Mr Jehyun Lee (Seoul National University)

7. Jehyun.pdf

4:00 PM → 6:00 PM Session3-Thu

4:00 PM Attractor mechanism : Trio of effective black hole potential, entropy functional and Routhian

In this talk we discuss various aspects of the effective dynamics of Maxwell-Einstein scalar theories in the background of static, spherically symmetric and extremal black hole solution in (1+3) dimensions. We show that the effective one dimensional action (governed by the Attractor mechanism) from which the effective black hole potential (introduced by Ferrara-Gibbons-Kallosh) is usually computed, is the one dimensional effective Routhian of the original (1+3)d action. We further discuss the interplay of this Routhian framework, black hole potential and Sen’s entropy functional approach, enabling one to compute the black hole entropy.

Speaker: Dr Sourav Roychowdhury (CQUeST, Sogang University)

8. Sourav Roychowdhury.pdf

4:30 PM Holography and Superstring Theory: 10D and 11D Supergravity

In this talk, I will discuss on-shell actions for type IIB supergravity and 11D M-Theory based on my recent papers (JHEP 06 (2026) 271 and 260X.XXXXX). In these works, we have consistently incorporated suitable topological terms that can be evaluated for a
large number of backgrounds. We also show that the on-shell actions for the original 10D and 11D supergravities obtained in our papers agree with the low-d wanted results. This consistency in the matching is important from the AdS/CFT point of view, since the free energy of boundary conformal field theory should match with the Euclidean
on-shell action of the effective supergravity. Our results thus place direct holographic comparisons within the ten-dimensional Type IIB and 11D M-theory framework on firmer ground. I will end my talk with some discussion.

Speaker: Dr Soumya Adhikari (CQUeST, Sogang University)

9. Soumya_CQUEST_July_Talk.pdf

5:00 PM Perturbation Theory of Nicolai Map for the 4D N = 1 Pure Supergravity

We present a perturbative construction of the Nicolai map for four-dimensional N = 1 pure supergravity around flat Minkowski space, as an alternative to the coupling-flow-operator approach. Using the second-order formalism and the background-field expansion of the vielbein in the gravitational coupling κ, we derive the on-shell BRST structure and formulate the defining conditions for a Nicolai map expanded in both κ and ℏ. We further recast the construction in a diagrammatic form that generates the most general local ansatz and reduces the problem to coupled nonlinear polynomial constraints. Applying the method to the gauge-fixed Einstein–Hilbert bosonic sector through second order in κ, we show that higher-order consistency is determined by the bosonic input and fixes the admissible lower-order fermionic couplings. These couplings agree with those of pure N = 1 supergravity, indicating a strongly constrained structure underlying the supergravity Nicolai map.

Speaker: Mr Jun Hyeok Lee (Hanyang University)

10. Jun hyeok Lee Perturbative Nicolai-Map Diagrammatics.pdf